/*
 *                               POK header
 *
 * The following file is a part of the POK project. Any modification should
 * be made according to the POK licence. You CANNOT use this file or a part
 * of a file for your own project.
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2021 POK team
 */

/* s_erff.c -- float version of s_erf.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#ifdef POK_NEEDS_LIBMATH

#include "math_private.h"
#include <libm.h>

static const float tiny = 1e-30, half = 5.0000000000e-01, /* 0x3F000000 */
    one = 1.0000000000e+00,                               /* 0x3F800000 */
    two = 2.0000000000e+00,                               /* 0x40000000 */
    /* c = (subfloat)0.84506291151 */
    erx = 8.4506291151e-01, /* 0x3f58560b */
    /*
     * Coefficients for approximation to  erf on [0,0.84375]
     */
    efx = 1.2837916613e-01,  /* 0x3e0375d4 */
    efx8 = 1.0270333290e+00, /* 0x3f8375d4 */
    pp0 = 1.2837916613e-01,  /* 0x3e0375d4 */
    pp1 = -3.2504209876e-01, /* 0xbea66beb */
    pp2 = -2.8481749818e-02, /* 0xbce9528f */
    pp3 = -5.7702702470e-03, /* 0xbbbd1489 */
    pp4 = -2.3763017452e-05, /* 0xb7c756b1 */
    qq1 = 3.9791721106e-01,  /* 0x3ecbbbce */
    qq2 = 6.5022252500e-02,  /* 0x3d852a63 */
    qq3 = 5.0813062117e-03,  /* 0x3ba68116 */
    qq4 = 1.3249473704e-04,  /* 0x390aee49 */
    qq5 = -3.9602282413e-06, /* 0xb684e21a */
    /*
     * Coefficients for approximation to  erf  in [0.84375,1.25]
     */
    pa0 = -2.3621185683e-03, /* 0xbb1acdc6 */
    pa1 = 4.1485610604e-01,  /* 0x3ed46805 */
    pa2 = -3.7220788002e-01, /* 0xbebe9208 */
    pa3 = 3.1834661961e-01,  /* 0x3ea2fe54 */
    pa4 = -1.1089469492e-01, /* 0xbde31cc2 */
    pa5 = 3.5478305072e-02,  /* 0x3d1151b3 */
    pa6 = -2.1663755178e-03, /* 0xbb0df9c0 */
    qa1 = 1.0642088205e-01,  /* 0x3dd9f331 */
    qa2 = 5.4039794207e-01,  /* 0x3f0a5785 */
    qa3 = 7.1828655899e-02,  /* 0x3d931ae7 */
    qa4 = 1.2617121637e-01,  /* 0x3e013307 */
    qa5 = 1.3637083583e-02,  /* 0x3c5f6e13 */
    qa6 = 1.1984500103e-02,  /* 0x3c445aa3 */
    /*
     * Coefficients for approximation to  erfc in [1.25,1/0.35]
     */
    ra0 = -9.8649440333e-03, /* 0xbc21a093 */
    ra1 = -6.9385856390e-01, /* 0xbf31a0b7 */
    ra2 = -1.0558626175e+01, /* 0xc128f022 */
    ra3 = -6.2375331879e+01, /* 0xc2798057 */
    ra4 = -1.6239666748e+02, /* 0xc322658c */
    ra5 = -1.8460508728e+02, /* 0xc3389ae7 */
    ra6 = -8.1287437439e+01, /* 0xc2a2932b */
    ra7 = -9.8143291473e+00, /* 0xc11d077e */
    sa1 = 1.9651271820e+01,  /* 0x419d35ce */
    sa2 = 1.3765776062e+02,  /* 0x4309a863 */
    sa3 = 4.3456588745e+02,  /* 0x43d9486f */
    sa4 = 6.4538726807e+02,  /* 0x442158c9 */
    sa5 = 4.2900814819e+02,  /* 0x43d6810b */
    sa6 = 1.0863500214e+02,  /* 0x42d9451f */
    sa7 = 6.5702495575e+00,  /* 0x40d23f7c */
    sa8 = -6.0424413532e-02, /* 0xbd777f97 */
    /*
     * Coefficients for approximation to  erfc in [1/.35,28]
     */
    rb0 = -9.8649431020e-03, /* 0xbc21a092 */
    rb1 = -7.9928326607e-01, /* 0xbf4c9dd4 */
    rb2 = -1.7757955551e+01, /* 0xc18e104b */
    rb3 = -1.6063638306e+02, /* 0xc320a2ea */
    rb4 = -6.3756646729e+02, /* 0xc41f6441 */
    rb5 = -1.0250950928e+03, /* 0xc480230b */
    rb6 = -4.8351919556e+02, /* 0xc3f1c275 */
    sb1 = 3.0338060379e+01,  /* 0x41f2b459 */
    sb2 = 3.2579251099e+02,  /* 0x43a2e571 */
    sb3 = 1.5367296143e+03,  /* 0x44c01759 */
    sb4 = 3.1998581543e+03,  /* 0x4547fdbb */
    sb5 = 2.5530502930e+03,  /* 0x451f90ce */
    sb6 = 4.7452853394e+02,  /* 0x43ed43a7 */
    sb7 = -2.2440952301e+01; /* 0xc1b38712 */

float erff(float x) {
  int32_t hx, ix, i;
  float R, S, P, Q, s, y, z, r;
  GET_FLOAT_WORD(hx, x);
  ix = hx & 0x7fffffff;
  if (ix >= 0x7f800000) { /* erf(nan)=nan */
    i = ((uint32_t)hx >> 31) << 1;
    return (float)(1 - i) + one / x; /* erf(+-inf)=+-1 */
  }

  if (ix < 0x3f580000) {   /* |x|<0.84375 */
    if (ix < 0x31800000) { /* |x|<2**-28 */
      if (ix < 0x04000000)
        /*avoid underflow */
        return (float)0.125 * ((float)8.0 * x + efx8 * x);
      return x + efx * x;
    }
    z = x * x;
    r = pp0 + z * (pp1 + z * (pp2 + z * (pp3 + z * pp4)));
    s = one + z * (qq1 + z * (qq2 + z * (qq3 + z * (qq4 + z * qq5))));
    y = r / s;
    return x + x * y;
  }
  if (ix < 0x3fa00000) { /* 0.84375 <= |x| < 1.25 */
    s = fabsf(x) - one;
    P = pa0 +
        s * (pa1 + s * (pa2 + s * (pa3 + s * (pa4 + s * (pa5 + s * pa6)))));
    Q = one +
        s * (qa1 + s * (qa2 + s * (qa3 + s * (qa4 + s * (qa5 + s * qa6)))));
    if (hx >= 0)
      return erx + P / Q;
    else
      return -erx - P / Q;
  }
  if (ix >= 0x40c00000) { /* inf>|x|>=6 */
    if (hx >= 0)
      return one - tiny;
    else
      return tiny - one;
  }
  x = fabsf(x);
  s = one / (x * x);
  if (ix < 0x4036DB6E) { /* |x| < 1/0.35 */
    R = ra0 +
        s * (ra1 +
             s * (ra2 +
                  s * (ra3 + s * (ra4 + s * (ra5 + s * (ra6 + s * ra7))))));
    S = one +
        s * (sa1 +
             s * (sa2 +
                  s * (sa3 +
                       s * (sa4 +
                            s * (sa5 + s * (sa6 + s * (sa7 + s * sa8)))))));
  } else { /* |x| >= 1/0.35 */
    R = rb0 +
        s * (rb1 + s * (rb2 + s * (rb3 + s * (rb4 + s * (rb5 + s * rb6)))));
    S = one +
        s * (sb1 +
             s * (sb2 +
                  s * (sb3 + s * (sb4 + s * (sb5 + s * (sb6 + s * sb7))))));
  }
  GET_FLOAT_WORD(ix, x);
  SET_FLOAT_WORD(z, ix & 0xfffff000);
  r = __ieee754_expf(-z * z - (float)0.5625) *
      __ieee754_expf((z - x) * (z + x) + R / S);
  if (hx >= 0)
    return one - r / x;
  else
    return r / x - one;
}

float erfcf(float x) {
  int32_t hx, ix;
  float R, S, P, Q, s, y, z, r;
  GET_FLOAT_WORD(hx, x);
  ix = hx & 0x7fffffff;
  if (ix >= 0x7f800000) { /* erfc(nan)=nan */
                          /* erfc(+-inf)=0,2 */
    return (float)(((uint32_t)hx >> 31) << 1) + one / x;
  }

  if (ix < 0x3f580000) { /* |x|<0.84375 */
    if (ix < 0x23800000) /* |x|<2**-56 */
      return one - x;
    z = x * x;
    r = pp0 + z * (pp1 + z * (pp2 + z * (pp3 + z * pp4)));
    s = one + z * (qq1 + z * (qq2 + z * (qq3 + z * (qq4 + z * qq5))));
    y = r / s;
    if (hx < 0x3e800000) { /* x<1/4 */
      return one - (x + x * y);
    } else {
      r = x * y;
      r += (x - half);
      return half - r;
    }
  }
  if (ix < 0x3fa00000) { /* 0.84375 <= |x| < 1.25 */
    s = fabsf(x) - one;
    P = pa0 +
        s * (pa1 + s * (pa2 + s * (pa3 + s * (pa4 + s * (pa5 + s * pa6)))));
    Q = one +
        s * (qa1 + s * (qa2 + s * (qa3 + s * (qa4 + s * (qa5 + s * qa6)))));
    if (hx >= 0) {
      z = one - erx;
      return z - P / Q;
    } else {
      z = erx + P / Q;
      return one + z;
    }
  }
  if (ix < 0x41e00000) { /* |x|<28 */
    x = fabsf(x);
    s = one / (x * x);
    if (ix < 0x4036DB6D) { /* |x| < 1/.35 ~ 2.857143*/
      R = ra0 +
          s * (ra1 +
               s * (ra2 +
                    s * (ra3 + s * (ra4 + s * (ra5 + s * (ra6 + s * ra7))))));
      S = one +
          s * (sa1 +
               s * (sa2 +
                    s * (sa3 +
                         s * (sa4 +
                              s * (sa5 + s * (sa6 + s * (sa7 + s * sa8)))))));
    } else { /* |x| >= 1/.35 ~ 2.857143 */
      if (hx < 0 && ix >= 0x40c00000)
        return two - tiny; /* x < -6 */
      R = rb0 +
          s * (rb1 + s * (rb2 + s * (rb3 + s * (rb4 + s * (rb5 + s * rb6)))));
      S = one +
          s * (sb1 +
               s * (sb2 +
                    s * (sb3 + s * (sb4 + s * (sb5 + s * (sb6 + s * sb7))))));
    }
    GET_FLOAT_WORD(ix, x);
    SET_FLOAT_WORD(z, ix & 0xfffff000);
    r = __ieee754_expf(-z * z - (float)0.5625) *
        __ieee754_expf((z - x) * (z + x) + R / S);
    if (hx > 0)
      return r / x;
    else
      return two - r / x;
  } else {
    if (hx > 0)
      return tiny * tiny;
    else
      return two - tiny;
  }
}

#endif
